Method of preparing 3, 3-disubstituted-6-dimethylamino-2-hexanones



Patented Oct. 20, 1953 OFFICE METHOD OF PREPARING 3,3-DISUBSTI- TUTED 6 DIMETHYLAMINO -2- HEXA- NONES.

Everett M. Schultz, Glenolden, Pa., assignor to Merck & 00., Inc., a corporation of New Jersey No Drawing. Application August 16, 1950, Serial No. 179,896

3 Claims.

This invention is concerned broadly with certain new chemical compounds and with methods for their preparation. The invention is more particularly concerned with new methods for the production of 3,3-disubstituted-6-dimethylamino- 2 hexanones, and 3,4,5,6 tetrahydropyridines methyl-substituted in the 2-position and disubstituted in the 3-position. Further, the invention is concerned with new substituted-2-hexanones obtained from the method of the invention. Additionally, the invention is concerned with new 3,4,5,G-tetrahydropyridines obtained as intermediate products in one step of the method of the invention.

The substituted-Z-hexanones of this invention can be represented by the formula:

(CHQIN O in which R is (1) alkyl up to and including lauryl, and preferably lower alkyl up to eight carbon atoms, and (2) mononuclear aralkyl, preferably benzyl, and Y is chosen from the group consisting of hydrogen, lower alkyl, halogen and alkoxy.

The tetrahydropyridines of this invention can be represented by the formula:

N/ OH:

in which R is (1) alkyl up to and including lauryl, and preferably lower alkyl up to eight carbon atoms (2) mononuclear aralkyl, preferably benzyl, and (3) mononuclear aryl, that is, C6H4Y, and in which Y is chosen from the group consisting of hydrogen, lower alkyl, halogen and alkoxy. Heretofore, 3,4,5,6 -tetrahydropyridines have been prepared by the cyclization of a o-aminoketone, which aminoketones are difiicult to obtain as the preparation is cumbersome and involved requiring several steps in the synthesis. Further, in the past, the hydrogenation of y-cyanoketones, the starting materials of this invention, has yielded only completely saturated cyclic compounds, that is, piperidines. It has beendiscovered, as a feature of this invention, that, in the presence of Raney nickel catalyst, 'y,'y-diSubstituted-o-oxocapronitriles can be hydrogenated so as to produce 3,4,5,fi-tetrahydropyridines, which intermediate compounds can be transformed to substituted-Z-hexanones on treatment 7 with formic acid and formaldehyde.

The complete process of this invention comprises hydrogenation of a -disubstituted-aoxocapronitrile in the presence of Raney nickel catalyst at approximately -100 C. and at approximately atmospheres pressure of hydrogen, to obtain 2-methyl-3,3-disubstituted-3,4,5,6 tetrahydropyridines. This step involves a feature of this invention and it is to be noted that the tetrahydropyridines so obtained are among the compounds of the invention. Thereafter, the tetrahydropyridines, which need not be isolated, upon treatment with formic acid and formaldehyde yield the desired, 3,3-disubstituted-6-dimethyl-amino-2-hexanones which are compounds of this invention. It is to be noted that this step involves a feature of this invention.

More particularly the hydrogenation step is carried out by admixing the appropriate oxocapronitrile (the preparation of which is described in my co-pending application entitled -Disubstituted-a-oxocapronitriles) in a solvent such as absolute methanol or ethanol, adding thereto Raney nickel catalyst in an amount of from 2 to 10 grams per mole of oxocapronitrile and exposing this mixture to an atmosphere of hydrogen with agitation in a suitable reaction vessel at a pressure of approximately 100 atmospheres and at a temperature of from approximately 90-400 C. In general, the reaction is completed within approximately 1 to 2 hours, although certain oxocapronitriles require longer reaction time. Under these conditions, the absorption of hydrogen ceases when two moles of hydrogen per mole of oxocapronitrile has been absorbed Utilizing the conditions of this invention and the Raney nickel catalyst, it has been discovered that little if any piperidine is formed and that substantially large proportions of the starting material is converted to the 3,4,5,6-tetrahydropyridine.

The above described hydrogenation is preferably carried out at 90-100" C. and at approximately 100 atmospheres pressure of hydrogen. It is to be noted that temperatures in excess of 100 C. will give decreased yields of the 3,4,5,6-tetrahydropyridines in that some of the tetrahydropyridine will be reduced further, that is, to the piperidine. It is to be realized that this hydrogenation can be carried out advantageously at" pressure less than 100 atmospheres as the reaction depends not so much upon the pressure as upon 7 the presence of hydrogen. Further, the temper-.

preferred since at lower temperatures the rate of reaction is correspondingly less.

The tetrahydropyridine need not be isolated, but the purity and ease of handling the resultant nq set ne ias li st y ur y n th tetrahydropyridine. tetrahydropyridine is dissolved innbmt to 10 moles, and preferably moles, of 90% formic acid per mole of tetra hydropyridine. To this is added trgrn 1 to 5 moles, and preferably 2.3 moles, of; 31%, elm-1911113; formaldehyde per mole of tetrahydropyridine and the entire mixture is heated on a steam bath until evolution of carbon dioxide. ceasesl evolution usually ceases in a period of timef-romt approximately 3 to hours, although thereac; tion for some compounds may fall outside-these particular limits. After the evolution of carbon dioxide has ceased the reaction mixture is re. moved from the steam bath, cooled, and hydrochloric. acids. n; amou t s iehtltassets i; 2%

st immater al is; adde t -C e he. hydrate. Saltthe rma e t. a ttien. an distille l-. to. ryness. under: vacu m at. ap Xi.- ma ly 100 0. i e esidue islta tsnfl fil s m n m m amount; Qt water; su t ier fiadieselr he-residue.- and. he oli t' eaweshedew th: ther until-1'. cle r.- 7

"marines-solut on Qt bezz sziaeqn here; ca

rota

hexanonesai l' a. m nes... wh ch. ompasses ehre elesisel ctivi .v o aamele. h aa-u is psmut g a 1 e i r esee sl.aeiise lirr rsicl act tityt.

'Dnesimze tion isl ir s r tedt a. bet Manatee: aril-y,.. e tr. cte .r t. h elicit n .nrefetr de mr bad me its mmi? ze r attfli mi; t. it ilmfi ifi- T I ,4. III-QIQL". vzmetht n O et- 4 st Rater ir e Q1 11. tha oh era la 'l"1 P@2 ack H r t flien;.- as.- 9 uos into. he. utocla ei aprs ser 1 3.

pou ds etseuare n @1 4 hwutaclave he s asaheatee wl mre 'eturs- 312M931: 1x997 1 nsirqe isder sea an -to. admit the contents. The heating was maintainedand h rm sine.. rr lleitie eni mleii; nti h s ak ihx rpe ea ees i hetaut cla e a 391S-11:9!?1 th n? ei eaeiiee ixtu e r m ve m r frbms nd. ltered 1 em t e ne nickel, catalyst. The ethanol was, evaporated from the. filtrate and the residue taken-up in approximately 106 ml. dilute hydrochloric acid. This aci d solation;was extracted with equal vol umes. off a e; in order to 3 remove unreacted nitr i l el The jrem ovalpfthe nitrile was evidenced at olution bee m'eesl eri; The o ut ns-e d sia i b QQWIE- d9XiQQ ;Wh 1 n n .-.S 1?erate his-oi 'iwas. ext acted with ether and the ether solution was dried over anhydrous potassium carbonate. The potassium carbonate was removed by filtration and the ether evaporated. The residue was further purified by distillation under vacuum and. there was obtained 2,3 dimethyl-3,-phenyl:3,l,5,6-tetrahydropyridine, Ba, F. 80-83 C; at 015; mm. Hg, 11 1.5437. The product was obtained in 81.5% yield. The bisulfate salt of this compound melts at 151.5453" 0.

rlidmple: 25-Erepdmtz'on of Z-methyZ-S-ethyl- 3*phenyl 435QEtetrahydropyridin.--USing the procedure outlined in Example 1 and a similar molar; mantity; of; 'y-ethyl-v-phenyl-o-oxocapronitrile. in: place. of; the 'y-methyl-v-phenyl-t-oxocapronitrile thereused, there was obtained a 71% ni -tri-le thera used .an vequimolar quantity. of. 77nbutyl- -phenykaeoxocapronitrile,; there was; ob.-. tained an 89 yield of 2-methyl-3-n-butyl-3- phenyl-3,4,5,6-tetrahydropyridine, B. P. 118.5 C. at 0.5 mm. Hg, 11. 1.5332. The bisulfate salt melts at 12l3 C.-

Other examples of the-preparation of Z-methyl-3-alkyl-3-phenyl- 3,4.5,6.- tetrahy-dropyridines will beapparentfrom considering that by substitnting for the -n-butylw-phenyle6-0xocapronitrile above used; equimolarquantities of v-noctyle'y phenykfi oxocapronitrile and 'y-n-lauryl y-phenykt oxocapronitrile there was obtained respectively 25-methyl-3-nroctyl-3epheny1 3;4;5,6 tetrahydropyridine and- 25-methyl-3-n-lauryl-3- phenyl-3,4,5,6-tetrahydropyridine.

Example 5--Preparation of 2-methyZ-3,3-diphenyl 3,4,5,6 tetrahydropyridine.Using the procedure outlinedsin Example 1 and substituting for the y-methyl v phenyl 6 oxooapronitrile there used an equimolar quantity of 'y,'y-dipheny1- soxocapronitrile there was obtainedv a,67% yield of 251nethy1-3;3;-*diphenyl-3;4;5;6=tetrahydropyri dine, l3. P;=128-30C. at-0.5 mm. Hg, IVER-106 7 C; The hydrochloride salt-melts at 20%209911 Egsgmple 6 -Preparation of 2'-"methyZ.-3--benzyl-' 35plzenyl 3,4; 5,6:tetmhydropyridine. Following the procedure in Exarnple liandsubstitutingjor the. 7 methyl -phenyl -doxocapronitrile there used; an equirnolar quantity," of 1' "/-.benzyl-" phenyl -t-oxocapronitrile there was obtained a 9%; yi d ..12 $.th 1,- yl- -ph y tetrahydrgpyridine Bg P; 137:'-9: C; at -0i5 mm: Hg, M; P;; 69; 5'-7Q'. 5"C: The hydroohloride'salt melts at 2I 8-=229 C. Thepicrate saltmeltsoat 1 other examples. birth invention will'be ap' parentjrom considering thatbyr substitutin for the ben zyl e henyl a, oxocapronitrile above used eql mqlar quantities of y-methyl-yeptolyl'e oxocapronitrile, 'y-n-propyl-y-p-chlorophenyl-6- oxocaproni'trile, y-ethyl- -p-isopropyl-phenyl-6- oxocapronitril 'Y D chlorobenzyl- -phenyl 6- oxacaprom'trile and v n propyl-'yp-methoxyphenyl-a-oxocapronitrile, there was obtained respectively 2,3-dimethy1-3-p-tolyl 3,4,5,6 tetrahydropyridine, 2,3 dimethyl-3-p-bromophenyl- 3,4,5,6-tetrahydropyridine, 2-methyl-3-n-propyl- 3-p-chlorophenyl-3,4,5,6 tetrahydropyridine, 2'- methyl-3-ethyl-3-p-isopropy1pheny1-3,4,5,6 tetrahydropyridine, 2 methyl-3-p-chlorobenzyl-3- phenyl-3,4,5,6-tetrahydropyridine and 2-methyl- 3-n-propyl-3-p-methoxyphenyl-3,4,5,6 tetrahydropyridine.

Example 7Preparation of 3-methyZ-3-phenyl- 6-dimethylamino-2-hemanone.-25 g. (0.134 mole) 2,3-dimethyl-3-phenyl-3,4,5,6-tetrahydropyridine (obtained as in Example 1) was dissolved with cooling in 36 g. (0.7 mole) 90% formic acid. To this was added 26 g. (0.31 mole) 37% formaldehyde. The reactants were heated on a steam bath for approximately three hours. The mixture was then cooled and there was added 25 ml. concentrated hydrochloric acid and the solution was vacuum distilled practically to dryness. There was added 100 ml. water and the resulting solution extracted once with an equal volume of ether. The water solution was then made alkaline with sodium hydroxide solution and a yellow oil precipitated. The oil was taken up in approximately 100 ml. ether and the ether solution dried over potassium carbonate. The potassium carbonate was separated from the ether solution by filtration and the ether evaporated. The residue was a yellow oil which was purified by vacuum distillation. There was obtained 13.8 g. of 3-methyl-3-phenyl-6-dimethylamino-Z-hexanone, B. P. 115 C. at 1.0 mm. Hg, 11. 1.5108. The hydrochloride salt melts at 1'77-8 C.

Example 8Preparation of 3-ethyZ-3-phenyl- 6-dz'methylamino 2 hemanona-Following the procedure outlined in Example '7, and substituting for the tetrahydropyridine there used an equimolar quantity of 2-methyl-3-ethyl-3-phenyl- 3,456-tetrahydropyridine (obtained as in Example 2) there was obtained 19 g. of 3-ethyl-3- phenyl-6-dimethylamino-2-hexanone, B. P. 104- 6 C. at 0.5-1.0 mm. Hg, n 1.5075. The hydrochloride salt melts at 166-7 C.

Example 9-Preparation of 3-n-propyZ-3-phenyl-6-dz'methylamino-Z-hexanona-Following the procedure outlined in Example '7 and substituting for the tetrahydropyridine there used an equimolar quantity of 2-methyl-3-n-propyl-3-phenyl-3,4,5,6-tetrahydropyridine (obtained as in Example 3) there was obtained 24 g. of 3-n-propyl- 3 phenyl 6 dimethylamino-2-hexanone, B. P. 121128 C. at 0.5 mm. Hg, n 1.5062. The hydrochloride salt melts at 193-l C.

Example 10Preparation of 3-n-butyZ-3-phenyZ-S-dimethyldmino-Z-hea:anone.Following the procedure outlined in Example '7 and substituting for the tetrahydropyridine there used an equimolar quantity of 2-methyl-3-n-butyl-3-phenyl- 3,4=,5,6-tetrahydropyridine (obtained as in Example 4) there was obtained 22.4 g. of 3-n-butyl- 3 phenyl 6 dimethylamino-Z-hexanone, B. P. 127-31 C. at 0.5 mm. Hg, 11. 1.5055. The hydrochloride salt melts at 151.5-153 C.

Example Iii-Preparation of 3-benzyZ-3-phenyZ-S-dimethylamino-2-hexanone.--Following the procedure outlined in Example 7 and substituting for the tetrahydropyridine there used an equimolar quantity of 2-methyl-3-benzyl-3-' phenyl-3,456-tetrahydropyridine (obtained as in Example 6) there was obtained 29 g. of-a benzyl-3-phenyl-6-dimethylamino 2 'hexanone, B. P. 157-60 C. at 0.5 mm. Hg. The hydrochloride salt melts at 205-6 C.

Other examples of the invention will be apparent from considering that by substituting for the tetrahydropyridine usedin Example 7 equimolar quantities of 2,3-dimethyl 3 p-tolyl- 3,456-tetrahydropyridine, 2,3 dimethyl 3 p bromophenyl-3,4,5,6-tetrahydropyridine, 2-methyl-3-n-propy1 -3-pchlorophenyl 3,4,5,6 tetrahydropyridine, 2methyl-3-ethyl-3-p-isopropy1- phenyl-3,455 tetrahydropyridine, 2 methyl-3- p-chlorobenzyl 3 phenyl 3,456 tetrahydropyridine and 2-methyl-3-n-propyl 3 p methoxyphenyl-3,4,5,6-tetrahydropyridine, there was obtained respectively 3-methyl-3-p-to1yl-6-dimethylamino-z-hexanone, 3-methyl-3-p-bromophenyl 6 dimethylamino 2 hexanone, 3 n propyl-3-p-chlorophenyl 6 dimethylamino 2-- hexanone, 3-ethyl 3 p isopropylpheny1-6-di-- methylamino-Z-hexanone, 3 p chlorobenzyl-3-- phenyl-6-dimethylamino-Z-hexanone and 3-npropyl-3-p-methoxyphenyl 6 dimethylamino 2-hexanone.

What is claimed is:

1. The method of preparing 3,3-disubstituted- 6-dimethylamino-2-hexanones having the general formula in which R is selected from the group consisting of an alkyl radical containing from 1 to 12 carbon atoms and a phenalkyl radical, and Y is selected from the group consisting of hydrogen, lower alkyl, halogen and alkoxy comprising hydrogenating an appropriate 'yfl-disubstituted-o-oxocapronitrile in the presence of Raney nickel catalyst at about -100 C. and at a pressure of about atmospheres, heating the tetrahydropyridine so formed with formic acid and formaldehyde until evolution of gas ceases, and recovering the 3,3-disubstituted-6-dimethylamino- Z-hexanone so formed.

2. In the method as claimed in claim 1 the step comprising hydrogenation of 'm-disubstituted-a-oxocapronitrile in the presence of Raney nickel catalyst at about 90-100 C. and at a pressure of about 100 atmospheres.

3. The method of preparing 3,3-disubstituted- 6-dimethylamino2hexanones having the general formula in which R is selected from the group consisting of an alkyl radical containing from 1 to 12 carbon atoms and a phenalkyl radical, and Y is selected from the group consisting of hydrogen, lower alkyl, halogen and alkoxy comprising dissolving an appropriate Yry-disubstituted-b oxocapronitrile in anhydrous ethanol, hydrogen ating said oxo'capronitrile in the presence 'of Raney nickel catalyst at 90-100 C. and at a pressure of 100 atmospheres hydrogemcooling the feas -ion ixtu e. se arati t catalyst theme;- 1mm a Ama Q; Sh m. 3 19if-rom, removing the .ethandl from the reaction 3, DR-

(1am, V *producma tetrahydmpyridine, treating the tetra.- .Kleidfler ,et a!" B3 Report 981, January 25,

hydropyridine with fmm 4 :to 10 moles iorm'ie 1911i 9p, 95:92, acid, and 1 to 5 moles formaldehyde per mole 5 Mgore, *Qggzgrgig: ,Rgagtions," ygl, ename 7, nforigi-nal eapronitrile, heating the reaction mix.- Wilfiy figngs, 9rk, N, 5]., ,9543,

tare at90+100 C. until evolution of gas ceases. filistke12 141., A1a t ag 9i punm mn ACS, and recevering the 3,3.-djsubstituted=fi=dimethyi- SK (1947), amino-2-hexwne so f rm d 13119:? at 11-, flhsm- 9Qfi 1.9%?! p.- 560- 19- 10 al-LT-aifibigs An en Ql- 55L PP- 52 8. =82 (1%3): BflH-mms i e in me fil of th inten 'Wnhl et 9.1, Berichte, v01. 43, DD. 3286-3294 (1910). 

1. THE METHOD OF PREPARING 3,3-DISUBSTITUTED6-DIMETHYLAMINO-2-HEXANONES HAVING THE GENERAL FORMULA 